Surgical Navigation System

ABSTRACT

A surgical navigation system is disclosed including a camera that is fixedly attached to a patient. The camera space merges with the patient space and thereby eliminates the need for a separate patient tracker. The surgical navigation system calculates the position of a surgical tool with a tracking device in view of the camera and shows on a display device the position of the surgical tool with respect to the patient superimposed and in correlation with a scan image of the patient.

BACKGROUND

1. Field of the Invention

The present invention relates to computer implemented navigation systemsused in surgical procedures.

2. Background of the Invention

Computerized surgical navigation systems are used to help guide asurgeon operating on a patient. In many instances, the use of navigationsystems enables the surgeon to perform a surgery on a patient in aminimally invasive manner. For example, a navigation system helps thesurgeon visualize or see the location of a surgical tool in relation toportions of the body that are not directly visible to the surgeon, suchas organs or bones on the inside of the body, by showing on a displayapparatus such as a television monitor or computer monitor the positionof the surgical tool in relation to the portion inside the body. Thus,smaller and/or fewer incisions into the body are needed because thesurgeon does not need a direct visual line of sight to a location ofinterest inside the body. Surgical navigation systems may also be usedin other types of surgery, such as an orthopedic procedure, to helpguide the surgeon while making cuts and/or placing objects on thepatient's bones, for example, in positions that have been planned andmarked with respect to pre-operative images taken of the body butwithout having to directly mark such locations on the patient's body.

There are many types of navigation systems that have been developed toassist with surgical procedures. In one well known exemplary navigationsystem, a multi-camera navigation system in communication with acomputer processor tracks tracking devices with LED's that flash andhave a known spatial configuration. One or more tracking devices calledtool trackers are attached to surgical tools in a known spatialconfiguration, and such information is located in a database availableto the computer processor. One or more tracking devices called patienttrackers are also attached in a fixed position to the patient, such aswith pins inserted into a bone. A set of two, three, or more trackingcameras, such as charge-coupled device (CCD) cameras, are located withinan operating room and are connected to the computer processor. The CCDcameras are positioned in a known, fixed relation with each other, suchas on a single bar, so that images from each of the three cameras may beprocessed and combined to triangulate the position of the trackers asviewed by the CCD cameras. In this system, the computer processor isused to concatenate several different position vectors includingpositional vectors from the cameras to the tool trackers and positionalvectors from the cameras to the patient trackers to track the positionof surgical tools with respect to the body. With appropriateregistration of various coordinate systems performed by the computerprocessor, the position of the tool may then be shown on a displaymonitor in registration with a scan image of the patient, such as anX-ray, ultra-sound, MRI, or CT scan image or the like, that showsvarious points of interest on the inside of the body. Although suchnavigation systems are highly effective in helping the surgeon navigatea tool inside the body without being able to see directly into the body,this system takes a large amount of computing resources in order to makethe required mathematical transformations of the various positionalvectors from the cameras to the tool trackers and the cameras to thepatient trackers. Although ongoing improvement in computing technologyreduces the amount of time necessary to make such calculations, becausethe navigation is performed in real time during the surgery, anyincrease in the speed of calculation such as by reducing the amount ofcomputing resources necessary would be desirable. Some exemplarysurgical navigation systems based generally on this type of technologyare disclosed in Chader U.S. Pat. No. 5,617,857, Schulz U.S. Pat. No.5,622,170, Faul et al. U.S. Pat. No. 6,497,134, Faul et al. U.S. Pat.No. 6,608,688, and Malackowski et al. U.S. Pat. No. 7,725,162, each ofwhich is incorporated in its entirety herein.

Another type of surgical navigation system includes a navigation camerais attached directly to a surgical tool for insertion into a patient'sbody. A target patch with optical navigation markers, printed thereon,is placed on the patient's body at or near a desired point of entry intothe body. The patch is registered with the body, and the camera viewsthe patch as the surgical tool is inserted into the patient's body. Thecamera is connected to a computer processor, which is programmed toprocess images of the optical navigation markers from the camera todetermine a position of the surgical tool in reference to the patch and,thereby, the patient's body. Thus, the computer processor is able toprocess the images of the patch with the navigation markers thereontaken by the camera to track the position of, for example, a tip of thesurgical tool that has been inserted in the body subcutaneously anddisplays such position on a computer monitor in registration with a scanimage of the area of interest. An example of such a system is disclosedin more detail in Gilboa U.S. Patent Application Publication No.2008/0208041, which is incorporated herein in its entirety. Althoughuseful for navigating the surgical tool, this surgical navigation systemrequires that each surgical tool has its own tracking camera attachedthereto and/or tracking patch for attachment to the patient's body thathas been adapted specifically for a particular use with a particularsurgical instrument and/or procedure. In addition, having a cameraplaced on the surgical tool itself may be cumbersome to the surgeon byadding weight or wires thereto.

Thus, the inventor of the present invention believes that it would beadvantageous to overcome one or more of the challenges of these priorart navigation systems, such as reducing the amount of computingresources necessary to track the position of the tool tracker withrespect to the patient's body and show such position in registrationwith a scan image of the body, removing cumbersome objects such ascameras from surgical tools, and providing a single system that may bereadily and easily adaptable for use with many different instruments andprocedures.

SUMMARY OF THE INVENTION

In one aspect of the invention, a surgical navigation system comprises acamera including means for attaching the camera in a fixed position to apatient, a surgical tool including a tracking element readable by thecamera, and a computer processing unit comprising means for recognizingthe tracking element in an image obtained by the camera and means fortracking the position of the surgical tool. A communication link isadapted to transmit images from the camera to the computerizedprocessing unit.

In another aspect of the invention, a surgical navigation cameracomprises a camera having a known focus, and means for attaching thecamera in a fixed position to a patient.

In a further aspect of the invention, a method of tracking a surgicaltool with respect to a patient comprises the steps of attaching a camerato the patient in a fixed position, and tracking a position of thesurgical tool in relation to the patient using pictures taken by thecamera and a computerized navigation system.

Other aspects and advantages of the present invention will becomeapparent upon consideration of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic depiction of a surgical navigation systemaccording to the invention;

FIG. 2 is another diagrammatic depiction of the surgical navigationsystem as used during a surgical procedure;

FIG. 3 is a flow chart of one method of using the surgical navigationsystem;

FIG. 4 is a flow chart of a method of using the surgical navigationsystem with an automatic registration procedure;

FIGS. 4A-4D illustrate various steps of the method of FIG. 4;

FIG. 5 is a flow chart of a method of using the surgical navigationsystem with a manual registration procedure; and

FIGS. 6 and 7 show the surgical navigation system as used in a differentsurgical procedure and with another attachment mechanism for anavigation camera.

DETAILED DESCRIPTION

Turning now to the drawings, a preferred embodiment of a navigationsystem 10 for providing navigation during surgery is shown in FIGS. 1and 2. The navigation system 10 includes a surgical tool 12 having atracking element 14 attached thereto, a camera assembly 16 having asurgical navigation camera 18 adapted to be fixedly attached to apatient 20, and a computer processing unit 22 for processing images fromthe camera 18 and displaying the surgical tool 12 in registration with ascan image of the patient on a display device 24.

The surgical tool 12 may be any tool used during surgery that can bemanipulated and arranged in a manner consistent with the purposes,functionality, and methods described herein. In FIGS. 1 and 2, thesurgical tool 12 is shown, for example, as a probe having a handle 26and a tip 28 for insertion into an incision or orifice of the body of apatient 20. Preferably, the surgical tool 12 has a known, pre-identifiedform factor, that is, the shape, size, and other spatial aspects ofinterest, such as an axis of the tool tip 28, which is stored in adatabase that may be accessed by the computer processing unit asdescribed hereinafter. Alternatively, the form factor of the surgicaltool 12 may be partially or completely unknown at the start of theprocedure, in which case the surgical tool 12 may be identified and/orcalibrated in additional steps and such information written to thedatabase. It is generally contemplated that the type of surgical toolsmost readily adapted for use with the navigation system 10 are hand heldtools, but the disclosure is not so limited, as it is clear that almostany type of tool that might be viewed by the camera 18 during a surgicalprocedure could be adapted for use with the navigation system 10.

The tracking element 14 includes an optical pattern that is readable bythe camera and adapted to be processed by a digital image recognitioncomputer program suitable for the uses and purposes described herein.The optical pattern is in a known, fixed position with respect to thetool tip 28, such that the position of the tool tip 28 can be determinedfrom a two-dimensional image of the tracking element 14 taken by thecamera 18. The optical pattern comprises passive markers, such ascolored ink markings. As used herein, the term “position” means spatialinformation regarding both the orientation of an object and location ordistance of the object from a given point. As shown in FIGS. 1 and 2,one possible optical pattern includes optical navigation markers 30 thatcan be viewed by the camera 18 and sensed by a digital image recognitionprogram employed by the computer processing unit 22. The trackingelement 14 is located where the optical navigation markers 30 will bevisible to the camera 18 during normal planned usage of the surgicaltool 12 during a given surgical procedure. Preferably, the position ofthe tracking element 14 on the surgical tool 12 is pre-defined andstored in the database. The tracking element 14 is dimensionally stable.In the present example, the tracking element 14 comprises a rigid orresilient substrate, such as a piece of plastic, cardboard, or metal,that is attached to the surgical tool 12 in a fixed or stable locationbetween the handle 26 and the tool tip 28, preferably near the tool tip28, with the optical navigation markers 30 oriented facing toward thetool tip 28 in order to be in position to be viewed by the camera 18while inserting the tool tip 28 into, for example, the patient's nasalpassageways to perform the surgical operation. This position of thetracking element 14 avoids disruptions of the line-of-sight between thecamera 18 and the tracking element 14 during relevant times in thesurgical procedure. The tracking element 14 may be permanently attachedto the surgical tool 12 or may be removable and re-attachable,preferably in a pre-selected position. The optical navigation markers 30on the tracking element 14 comprise a set of shapes and/or colors thatcan uniquely identify the position and/or identity of the surgical tool12 when viewed from any viewing angle by the camera 18. For example, theoptical navigation markers 30 have three separate shapes in pre-selectedpositions on the substrate, including a triangle, a square, and acircle, and each optical navigation marker 30 has a different color. Theoptical navigation markers 30 could take other shapes and/or colors thatare able to uniquely identify the position of the tracking element in atwo-dimensional image thereof, such as and without limitation, pinkhearts, yellow moons, orange stars, and/or green clovers. The opticalnavigation markers 30 may also have different colors and/or patternsand/or other visually readable cues that are visually readable to thecamera 18 and that can be used to uniquely identify the position and/oridentity of the surgical tool 12. The optical navigation markers 30 areconsidered to be passive markers in that they do not emit their ownenergy. However, in other applications, the tracking element 14 mayinclude active markers, such as LEDs and/or other types of navigationmarkers that may be sensed by the camera 18. The surgical tool 12 andtracking element 14 are pre-calibrated, whereby the position of thetracking element 14 with respect to the camera assembly 16 may also beautomatically identified based on the size and orientation of theoptical navigation markers 30 in images obtained from the camera 18. Theoptical pattern also uniquely identifies the surgical tool 12 with formfactor data relative to the surgical tool 12 stored in the database.Specifically, the optical navigation markers 30 provide uniqueinformation regarding both position and identity of the surgical tool12. Alternatively, the optical pattern on the tracking element 14 may bedivided into two independent portions, wherein a first portion includesa localization pattern including a set of generic navigation markers 30that may be used for positional tracking, i.e., localization, of severaldifferent tools, and a second portion includes an identification patternincluding a separate identification marker that uniquely identifies eachsurgical tool 12. The identification marker may be any opticalidentifier, such as a number, bar code, or other symbol that canuniquely identify the identity of the surgical tool 12 to the computerprocessing unit 22. In this instance, the identification marker is usedto access form factor information about the surgical tool 22, and thenavigation markers are calibrated with respect to the form factor ofthat particular surgical tool. In this example, several different toolsmay use the same localization pattern, and each tool may have adifferent identification pattern that uniquely identifies the tool.

The surgical tool 12 preferably is not physically connected to thecamera assembly 16 or to any other instruments, such as by wires. Thus,for example, the surgical tool 12 can be considered to be wirelessbecause it does not have a wired connection to other components of thenavigation system 10. Of course, a surgical tool 12 may include internalwiring for such things as internal circuitry for other structures and/orfunctions that are contained wholly in the surgical tool. However, thenavigation system 10 may have wired connections to other instruments. Inaddition, the surgical tool 12 with the tracking element 14 with apassive optical pattern may be lighter than a tracking element with LEDsor other heavier structures, and thereby be easier to use during thesurgical procedure.

The camera 18 has a completely known focal geometry. The camera 18 is anoptical video camera that has a fixed focus lens, which has a focalgeometry, including a focal length, focal plane, and focal axis that isfixed with respect to the camera 18 and/or the camera assembly 16 andknown to the computer processing unit 22. Thereby, images taken by thecamera 18 have a constant relation with respect to the body of thecamera 18 and thus a camera coordinate system 32 associated with thecamera (also called the “camera space”). Alternatively, the camera 18may have a changeable focal geometry, such as with a zoom lens, if thefocal geometry is determinable and known when tracking.

The camera assembly 16 also includes means for attaching the camera 18to the patient 20 in a stable, fixed position relative to a surroundingregion of the patient 20, and fiducial marks, such as fiducial markers34, and one or more validation features 36. The camera assembly 16 ispreferably small enough to allow for movement and repositioning of thepatient 20 while the camera assembly 16 is attached thereto. Further thecamera assembly 16 can be packaged and delivered in a sterile conditionfor immediate use in the surgical procedure without the need tosterilize or drape the camera assembly 16 at the hospital. The cameraassembly 16 is also preferably, small, lightweight, and relativelyinexpensive so as to be suitable for single use and thereby rendercumbersome reprocessing by a hospital unnecessary.

The attachment means may take any form suitable for use to fixedlyattach the camera 18 to the patient 20 during a surgical procedurewithout unduly harming the patient 20 and that allows the camera 18 tobe readily removed from the patient 20 at the completion of the surgicalprocedure. In the examples shown in FIGS. 1, 2, and 4A-4D, theattachment means includes a resilient substrate, such a base plate 38made of metal or hard plastic plate, which is attached to the camera 18.The camera 18 is attached to the base plate 38 in a fixed known positionsuch that the orientation of the base plate 38 is unchanging withrespect to the orientation of the camera 18. The camera 18 is disposedon one side of the base plate 38, such as the top side as shown in FIG.1, and an adhesive 40 is spread over the opposite side of the base plate38, such as the bottom side shown in FIG. 1. A protective covering 42,such as a release liner, covers the adhesive 40 to protect the adhesive40 before it is desired to expose the adhesive 40 for attaching the baseplate 38 to the patient 20. The protective covering 42 may be removedjust prior to securing the camera assembly 16 to the patient 20. Theadhesive 40 is preferably sufficient to securely attach the base plate38 to the skin of the patient 20 in a fixed manner and also allowremoval of the base plate 38 thereafter without causing undue harm tothe patient's skin, thereby allowing for non-invasive attachment of thecamera assembly 16 to the patient 20. Other means for attaching thecamera 18 to the patient may include straps, clamps, pins, screws,clips, and other mechanisms with appropriate functionality. For example,in some instances, the camera 18 without the base plate 38 is attacheddirectly to the patient 20 with adhesive 40, or the camera 18 is clampedto the patient 20 such as with clamps, straps, or any other type ofattachment mechanism suitable for use in surgical situations. Ifdesired, invasive attachment mechanisms, such as pins or screws, may beused. Other forms of attachment mechanisms may be particularlyadvantageous in embodiments where the fiducial markers 34 are notpresent at all or are integrated with the body of the camera 18 itself.

According to one optional aspect, the fiducial markers 34 are disposedon the base plate 38 in known positions around the camera 18 insufficient number and location that the fiducial markers 34 may be usedto identify the position of the camera 18 and camera coordinate system32 from an image of the camera assembly 16. In one instance, the cameraassembly 16 includes a plurality, preferably three or more, fiducialmarkers 34, such as metal balls, targets, or other known types offiducial markers that can be identified in visual light, CT scan, MRI,X-ray, and/or other types of imaging modalities. In another aspect, thefiducial markers 34 may comprise preselected and identifiable shapesand/or objects directly on the body of the camera 18. As shown in FIG.1, the fiducial markers 34 comprise metal balls, which are visible inmost applicable imaging modalities, disposed directly on the top side ofthe base plate 38 in positions selected to maximize the ability andaccuracy of triangulation calculations that will be based thereon, suchas nearly an equilateral triangle or a right triangle as shown inFIG. 1. The metal balls are preferably in a fixed, known position withrespect to the camera 18 and thus with respect to the focal geometry,the images taken by the camera 18, and the camera coordinate system 32.In this manner, the camera assembly 16 may itself be used forregistration of the camera space with a scan image of the patient'sbody.

The validation feature 36 is an optional feature for validating and/orcalibrating the surgical tool 12. As used herein, validation encompassesa procedure that checks whether the geometry, i.e., the form factor, ofthe surgical tool 12 is within a pre-defined tolerated range of error.For example, a validation of the surgical tool 12 checks whether thetool tip 28 is within a pre-defined tolerated distance of thetheoretical position as defined in the database and either accepts orrejects the surgical tool 12. Also as used herein, calibration is aprocedure that defines the geometry of the surgical tool 12, and mostfrequently the position of the tool tip 28, with respect to the trackingelement 14. The validation feature 36 may take any suitable form forvalidating or calibrating the surgical tool 12. In one instance as shownin FIG. 1, the validation feature 36 comprises a known predefinedposition on the camera assembly 16 such as a point shown or demarcatedby an “X” on the base plate 38. The validation feature 36 is located ata fixed, known position on the camera assembly 16 such that the trackingelement 14 of the surgical tool 12 is clearly visible to the camera 18when the tool tip 28 is positioned on the validation feature 36 during avalidation or calibration procedure. The validation feature 36 also canbe used for calibration and re-calibration of the surgical tool 12. Thevalidation and calibration procedures may be performed by suitablehardware and/or software on the computer processing unit 22 in a mannerknown and/or readily perceived by a person skilled in the art.

Preferably, the camera 18 and the markers 34 are fixedly attached to thebase plate 38 so that the camera 18 and camera coordinate system 32 arein a known, fixed position with respect to the markers 34. In someembodiments, however, the camera 18 is separable from the base plate 38and can be reassembled only in a predefined spatial relationshipthereto. The camera 18 is releasably attached to the base plate 38 witha specially adapted connector, such as a directional quick-releaseconnector, which ensures that the camera 18 can be removed andre-attached in only a single location and orientation. With thisfeature, the base plate 38 with the fiducial markers 34 can be scannedwith the patient, and the camera can be attached thereafter when moreconvenient. In another embodiment, each fiducial marker 34 is alsoreleasably attached to the base plate 38 by a specially adaptedconnector, such as a directional quick-release connector or a threadedstud, which ensures that the fiducial markers 34 are reattached in onlya single location and/or orientation. This provides the same advantageof having a known spatial relation between the fiducial markers 34 andthe camera coordinate system 32, and further may improve ease ofhandling during imaging and make it easier to maintain sterility duringthe surgical procedure.

The camera 18 is in communication with the computer processing unit 22by a data communication link 44 that electronically transmits imagesobtained from the camera to the computer processor. As shown in FIGS. 1and 2, the camera assembly 16 includes a hard-wire data communicationlink 44 for communicating images from the camera 18 to the computerprocessing unit 22. However, any other types of communication links 44that are suitable for transmitting the image data from the camera 18 tothe computer processing unit 22 may alternatively be used, such asvarious known wireless data transmission mechanisms, includinginfra-red, radio frequency, and blue-tooth data communication systems.

The computer processing unit 22 includes a computer processor 46 adaptedwith hardware and/or software programming that cause the computerprocessor 46 to read images of the tracking element 14 from the camera18 and show the position of the surgical tool 12 in registration with ascan image 48 of the patient on the display device 24 from such images.The computer processor 46 may include any hardware and softwarearchitecture sufficient to engage in the various processing stepsrequired by the navigation system 10. For example, the computerprocessor 46 may comprise a single computer, such as a microcomputer orserver, or the processor may comprise multiple interconnected datastorage and processing units, such as an internet-based processingsystem located on several disparate but interconnected computers. Thescan image 48 may be any image useful to the surgeon to plan and/orexecute the surgical procedure, and will generally include suchmodalities as a CT, ultra-sound, X-ray, MRI, infra-red, visiblespectrum, and any other imaging modality suitable for use with surgicalprocedures. Often, the scan image 48 includes image data relative tosubcutaneous structures in the patient's body, such as organs, bones,tumors, cancers, blood clots, and/or other items of interest inside thepatient's body.

The computer processor 46 is in communication with the camera 18, thedisplay device 24, and input/output devices 50, such as a keyboard,mouse, digitizer, printer, etc. The computer processor 46 also comprisesvarious hardware and/or software modules or functionalities that adaptthe computer processing unit 22 to function as required for thenavigation system 10. Thus, the computer processor 46 includes in somemanner the following functional components: digital memory that containsthe scan image 48 of the patient 20; a database 52 comprisinginformation on the form factor of the surgical tool 12 and trackingelements 14; a digital image recognition module 54 for parsing imagesreceived from the camera 18 and identifying various informationtherefrom, such as the position of the optical navigation markers 30 onthe tracking element 14 and location of the tracking element from thecamera 18; a registration module 56 for registering the camera 18 and/orthe patient 20 with the scan image 48; a tracking module 58 forconcatenating position vectors to show an image of a tracked surgicaltool 12 in correlation with the scan image 48 on the display device 24in real time; and a display functionality for displaying the variousinformation on the display device 24. The software and hardwarecomprising the computer processing unit 22 may be adapted from any suchgenerally available software and hardware, and the present disclosure isnot limited to any particular such type of processing capabilities.

The database 52 is associated with the computer processing unit 22 inany suitable manner whereby the computer processor 46 can access thedatabase 52. The database 52 may be any digital database systemcompatible for interaction with the computer processor 46 and associatedhardware and software, and, for example, may be stored on-site oroff-site, may be commercially available or proprietary. The database 52preferably includes information regarding specific surgical tools 12,such as the form factor of a tool and positional and identifyinginformation on the tracking element 14. The database 52 also preferablyincludes information regarding the camera assembly 16, such as basicform factor information relative to the fiducial markers 34 and thecamera space. Of course, the database 52 may include other usefulinformation, such as patient information, information relevant to asurgical procedure to be performed, etc.

The digital image recognition module 54 comprises means for determininga position of the surgical tool 12 with respect to the camera 18, andincludes appropriate software and/or hardware algorithms implemented bythe computer processor 46 that extract and calculate a position of thetracking element 14 with respect to the camera 18 from an image of theoptical navigation markers 30 taken by the camera 18. Many digital imagerecognition software programs are known and any such program that isable to perform the necessary processes and functionality is sufficient.Preferably, the digital image recognition module 54 is capable ofdetermining the position of the surgical tool 12 from a two-dimensionalimage of the tracking element 14 visible to the camera 18 by, forexample, comparing the image of the optical navigation markers 30 withthe form factor data of both the surgical tool 12 and the opticalnavigation markers 30 available from the database 52. Thus, because theoptical navigation markers 30 have a unique two-dimensional imagethereof from every possible viewing angle, the position of the trackingelement 14 and the surgical tool 12 with respect to the camera 18 can becalculated from a single two-dimensional image thereof, which may beperformed in a manner well-known in the art.

The registration module 56 comprises means for registering the cameracoordinate system 32 with the scan image coordinate system 60 to be ableto show the position of the surgical tool 12 in relation to the patient20 in correlation with the scan image 48 of the patient on the displaydevice 24. Many suitable registration functions and methods are known inthe art and may be adapted for use with the navigation system 10 andmethods described herein. Preferably, the registration module 56 isadapted to automatically register the camera 18 with the scan image 48without any user interaction when the scan image 48 includes the regionof interest of the patient and the camera assembly 16 rigidly attachedto the patient 20. Alternatively or additionally, the registrationmodule 56 is adapted to facilitate manual registration of the camera 18with the scan image 48, in which case it may not be necessary for thefiducial markers 34 or the camera 18 to be visible in the scan image 48.Exemplary methods of both automatically and manually registering thecamera 18 with the scan image 48 are described in more detailhereinafter.

The tracking module 58 comprises means for determining the position ofthe surgical tool 12 in relation to the patient 20 and combining suchposition superimposed and in registration with the scan image 48 of thepatient 20 for showing on the display device 24. Any known computerprogramming capable of making such known mathematical transformationsmay be used. For example, the tracking module 58 may include a softwareand/or hardware algorithm that concatenate the position information fromthe digital image recognition module 54 in combination with form factorinformation from the database 52 and registration vectors from theregistration module 56 to show the surgical tool 12 on the displaydevice 24 in correlation with the scan image 48. Such registrationgenerally is performed by known positional vector concatenationtechniques, including positional vectors from the camera 18 to thesurgical tool 12, and positional vectors of the camera 18 with respectto points on the patient 20 for example. Such mathematicaltransformations are well-known in the art and need not be discussedfurther herein. An advantage of the present navigation system 10 is thatthe algorithm for performing the concatenation calculations does nothave to concatenate a positional vector from a tracking camera to apatient tracker attached to the patient 20 and used solely to identifythe position of the patient 20 with respect to the navigation camera.Rather, fixedly attaching the camera assembly 16 directly to the patient20 effectively eliminates the need for a patient tracker that isseparate and independent from the navigation camera because the cameracoordinate system 32 is directly correlated with the patient's body inthe scan image 48, which reduces the number of coordinatetransformations required during navigation and leads to fasterperformance and higher precision of navigation.

The various computer modules 54, 56, 58 described herein are describedas modules only for the sake of simplicity of description. In fact, thefunctionalities described may be performed in any suitable hardwareand/or software architecture capable of determining the orientation ofthe surgical tool 12 from a two-dimensional image of the trackingelement 14 visible to the camera 18 and showing such orientation on thedisplay device 24 in registration with the scan image 48 of the patient20. In this manner, the computer processing unit 22 with any one of thevarious modules and/or hardware and software combinations describedherein comprises a computer means for tracking the surgical tool, andthe aggregate of the software programs comprising the modules 54, 56, 58may be called simply the navigation software.

The computer processing unit 22 is in communication with the displaydevice 24, which may be any device sufficient to display the position ofthe surgical tool 12 superimposed with and in correlation with the scanimage 48 of the patient 20, such as a computer monitor, television,projector, and/or paper printout from a printer. Preferably, the scanimage 48 includes image data portions inside the body of the patient 20that may not be visible to the surgeon or to the camera 18 so that thedisplay image 48 can show the position of the surgical tool 12 withrespect to those portions of the patient's body that are not directlyvisible to the surgeon. In this manner, the display can display theposition of the surgical tool 12 with respect to hidden portions of thepatient's body in real time as the surgeon manipulates the surgical tool12 during the surgical procedure.

Turning now to FIGS. 2 and 3, a general method of using the navigationsystem 10 includes steps of attaching the camera assembly 16 to thepatient 20, registering the camera 18 with the scan image 48 of thepatient 20, tracking the position of the surgical tool 12 using thecamera 18 and displaying the position of the surgical tool 12 withrespect to the patient 20 in correlation with and superimposed over thescan image 48 on the display device 24.

At a block 80, the camera assembly 16 is attached to the patient 20 bythe adhesive 40 on the bottom of the base plate 38 in a fixed positionsuch that the camera coordinate system 32 does not move in relation tosurrounding areas of the patient 20. Preferably, the camera assembly 16is small enough to allow the patient 20 to be moved and repositioned bythe surgeon as desired while the camera assembly 16 is attached to thepatient 20. The camera assembly 16 is fixed to the body with the lensdirected to view a region encompassing an expected area of activityduring the surgical procedure. For example in an ear, nose, throatsurgical procedure, as shown in FIG. 2, it is anticipated that thegeneral activity will include inserting the tool tip 28 through thenasal cavity of the patient 20 to a target location 62 (shown inphantom) in an interior portion of the patient's head. Therefore, thecamera assembly 16 is fixedly attached to the skin of the foreheadand/or the skull of the patient 20 with the camera lens oriented to havea field of view that encompasses the region above the patient's nose andmouth where the surgical tool 12 is expected to be manipulated duringthe surgical procedure. When so attached, the camera 18 is fixedrelative to the surrounding portions of the patient 20, such as theskull, nasal cavities, and the brain, thereby also fixing the cameracoordinate system 32, and preferably the focal geometry, with respect tothe surrounding or adjacent areas of the patient's body.

At a block 82, the position of the camera 18 is registered with theposition of the patient 20 in a scan image 48. The registrationprocedure may be performed in any of many different manners and methodsknown for registering one coordinate system with another. Some specificor preferred automatic and manual methods of conducting suchregistration are discussed in detail hereinafter. Of particularrelevance at this point, however, is that upon registration of thecamera space with the scan image space, the relationship between thecamera coordinate system 32 and the scan image coordinate system 60 isknown sufficiently to be able to calculate and show the position of thesurgical tool 12 with respect to the patient 20 in correlation with thescan image 48 on the display 24.

Upon registration of the camera 18 with the scan image 48, the surgicaltool 12 with the tracking element 14 is introduced within the field ofview of the camera 18, and a block 84 tracks the position of thesurgical tool 12 by means of the navigation software, which shows suchposition on the display monitor 24 in relation to the scan image 48 atblock 86. Thus, for example, as a surgeon manipulates the surgical tool12 through the nasal cavities of the patient 20, the location of thetool tip 28 inside the patient's head is shown on the display monitor 24in correlated relation to the scan image 48, thereby effectivelyallowing the surgeon to see on the display device where the surgicaltool 12 is in relation to the target location 62 inside the patient 20.

The step of registering the camera with the scan image of the patientperformed at block 82 may be performing automatically or it may beperformed manually using the registration module 56 of the navigationsoftware.

In FIG. 4, a method of using the navigation system using an automaticregistration procedure is shown. In this method, the camera assembly 16includes fiducial markers 34 that are sufficient to allow the positionof the camera 18 to be uniquely identified by the navigation software.

At block 100, the camera assembly 16 is attached to the patient 20 in afixed position with respect to surrounding portions of the patient'sbody, as shown in FIG. 4A, with the adhesive 40.

At block 102, a scan image 48 of the patient 20 is obtained with thecamera assembly 16 secured to the patient 20, wherein the scan image 48includes the camera assembly 16 as attached to the patient's body withthe fiducial markers 34 visible. An exemplary scan image 48 so obtainedis shown in FIG. 4B, which shows the camera assembly 16 attached to theskull of a patient 20 and the fiducial markers 34 of the camera assembly16 visible in the scan image 48.

At block 104, the navigation software automatically recognizes andidentifies the fiducial markers 34 visible in the scan image 48.

At block 106, the navigation software calculates the position of thecamera assembly 16 from the position of the fiducial markers 34 in thescan image 48. The position of the fiducial markers 34 with respect tothe camera coordinate system 32 and to the focal geometry of the camera30 is known from form factor information retrieved from the database 52.

At block 108, the navigation software automatically registers the cameraspace with respect to the position of the patient 20 in the scan image48 by identifying the position of the camera coordinate system 32 withinthe scan image 48. Because the patient 20 is fixedly connected to thecamera assembly 16, the scan image coordinate system 60 is alreadydirectly correlated with the camera coordinates system 32. Theregistration module 56 automatically performs a coordinatetransformation calculation as appropriate and thereby transforms thescan image coordinate system 60 into the camera coordinate system 32 orvice versa. Thereafter, the camera space is registered, or merged, withthe scan image space, i.e., the positions of the camera 18 and the scanimage 48 of the patient 20 are both known in relation to a singlecoordinate system, such as the camera coordinate system 32. Uponautomatic registration of the camera 18, tracking of the surgical tool12 is immediately available through the known relationships between thesurgical tool 12, the camera coordinate system 32, the scan imagecoordinate system 60, and form factor information of the surgical tool12 from the database 52.

At block 110, the surgical tool 12 is introduced into the view of thecamera 18, as shown in FIGS. 4C and 4D. The tracking element 14, asviewed from the camera 18 (shown in FIG. 4D), identifies the surgicaltool 12 to the navigation software, which retrieves the relevant formfactor information from the database 52 and calculates the position ofthe surgical tool 12 with respect to the camera coordinate system 32using the digital image recognition module 54 as discussed previously.

Advantageously, the navigation software does not have to recalculate thetransformation between the camera coordinate system 32 and the scanimage coordinate system 60 because the camera 18 does not move relativeto the patient 20 after the registration procedure until after thesurgical procedure is completed. In a preferred embodiment, for example,the scan image 48, which initially is in the scan image coordinatesystem 60, is transformed into the camera coordinate system 32 a singletime during registration and is not recalculated thereafter. Therefore,during navigation, it is only necessary to update the positional vectorof the surgical tool 12 relative to the camera coordinate system 32whenever the surgical tool 12 moves relative to the camera 18. Thus, thenavigation system 10 provides a significant reduction of computingresources over prior art navigation systems where the camera space isnot fixedly correlated to the patient.

At block 112, a validation procedure is performed to verify whether thesurgical tool 12 is within a pre-defined acceptable error range from theform factor information in the database 52. In one method, the tool tip28 is placed on the validation feature 36 with the optical navigationmarkers 30 in the field of view of the camera 18. The surgical tool 12is identified, relevant form factor information for the surgical tool 12is retrieved from the database 52, and the theoretical position of thetool tip 28 is calculated from the retrieved form factor information.The theoretical position of the tool tip 28 is compared to the actualposition of the tool tip 28 on the validation feature 36. If thetheoretical position and the actual position of the tool tip 28 arewithin a pre-defined acceptable error distance of each other, then thesurgical tool 12 is verified as acceptable for use in the surgicalprocedure and control passes to a block 114 for tracking and displayingthe surgical tool 12. If the theoretical position and the actualposition of the tool tip 28 are not within the pre-defined acceptableerror distance of each other, then the surgical tool 12 is rejected foruse in the surgical procedure and control passes to block 116.

At block 116, a decision is made whether to replace the surgical tool 12with a different surgical tool 12 or to calibrate the surgical tool 12.If a new surgical tool 12 is selected, the procedure returns to block110 and repeats. If, alternatively, it is decided to continue using thesame tool 12, the procedure commences to block 118 for performing acalibration procedure.

At block 118, a calibration procedure is performed, wherein the formfactor of the surgical tool 12 in relation to the tracking element 14 iscalculated and written back to the database 52. In one method, the tooltip 28 is placed on the validation feature 36 with the opticalnavigation markers 30 in the field of view of the camera 18. Thesurgical tool 12 is identified by the tracking element 14, and relevantform factor information for the surgical tool 12 is written into thedatabase 52. The position of the tracking element 14 with respect to theactual position of the tool tip 28 on the validation feature 36 iscalculated, and that position information is written to the database 52for use during subsequent tracking. After the surgical tool 12 has beencalibrated, the surgical tool 12 preferably is again validated at block112, and the procedure continues from there. In some circumstances, thecalibration procedure may be necessary if there is not sufficientpre-defined form factor information in the database 52, in which casethe calibration procedure may be an additional or alternative part ofthe validation procedure.

After performing the automatic registration, validation, and optionalcalibration procedures, the surgical procedure commences with completetracking of the surgical tool 12 from the single camera 18 as thesurgical procedure is performed. At block 114, the computer processingunit 22 displays or causes to be displayed the relative position of thesurgical tool 12 to the patient 20 in registration with the scan image48 shown on the display device 24.

Additional surgical tools 12 may be tracked by the camera 18 during thesame surgical procedure. Each surgical tool 12 has a tracking element 14with a unique set of optical navigation markers 30, i.e., havingdifferent shapes, colors, and/or spacing, which are stored in thedatabase 52 and uniquely identify each surgical tool 12 to thenavigation software. Alternatively, as described above, each trackingelement 14 may include the same optical navigation markers 30 forpositional tracking, and also include a unique optical identificationmarker that indicates the identity of the surgical tool 12.

Turning now to FIG. 5, the navigation system 10 may also oralternatively be adapted to manually register the camera 18 with thescan image 48. Although the scan image 48 may be obtained with thecamera assembly 16 already attached to the patient 20 as in FIG. 4B, amanual registration procedure is particularly useful when, for example,the camera assembly 16 is not already attached to the patient 20 whenthe scan image 48 is obtained or where the camera assembly 16 does notinclude fiducial markers 34. In this method, it is not necessary to beable to identify the fiducial markers 34 in the scan image 48.

In a method of using the navigation system 10 including a manualregistration procedure, a scan image of the patient 20 is obtained at ablock 120. The scan image is obtained without an image of the cameraassembly 16 therein and thus may be taken before the camera 18 isattached to the patient 20.

At block 122, the camera assembly 16 is attached to the body of thepatient 20, and the scan image is imported into the computer processingunit 22. Preferably, the camera assembly 16 is attached to a portion ofthe patient 20 that will not move in relation to the scanned portion ofthe patient during the surgical procedure.

At block 124, a registration tool is validated and/or calibrated withrespect to the position of the camera 18. In one method, the surgicaltool 12 is used as a registration tool. Alternatively, a separate tool,such as a pointer (not shown), is used as a registration tool.Validation of the registration tool may be completed in any manner knownin the art. Preferably, the validation is performed automatically basedon form factor information in the database 52, as described previouslywith respect to block 112 of FIG. 4. Alternatively or additionally, theregistration tool may be calibrated (or recalibrated) at block 124 asdescribed previously with respect to block 118 of FIG. 4. The validationand/or calibration of the registration tool preferably are performedusing the validation feature 36 as described previously herein.

At block 126, the registration tool, such as the surgical tool 12, isused to locate points on the body of the patient 20 while tracking theregistration tool with the camera 18. The points located may includespecific physical landmarks and/or a cloud of points on a surfaceidentifiable in the scan image 48 for performing a registrationcalculation.

At block 128, the camera 18 is registered with the scan image 48 bymatching points located on the body at block 126 to correspondingportions of the scan image 48 of the patient 20 by any method sufficienttherefore, such as by performing a point-to-point registration procedureand/or a surface matching registration procedure, and performingappropriate coordinate transformations. In a point-to-point registrationprocedure, physical landmarks located at block 126 are matched withcorresponding structures in the scan image 48. Thereafter, apoint-to-point registration procedure is performed to register thecamera space with the scan image space by, for example, a point-to-pointmatching procedure and appropriate coordinate transformations known inthe art. In a surface matching registration procedure, the cloud ofpoints located at block 126 is matched to the corresponding surfacevisible in the scan image 48 by, for example, a surface matchingprocedure and appropriate coordinate transformations known in the art.

At block 130, if a surgical tool different from the tool used toregister the scan image will be used to perform the surgical procedure,the new tool preferably is validated. The validation procedure at block130 preferably is identical to the validation procedures alreadydescribed herein and may be omitted if the same surgical tool is usedduring the procedure that was already validated at block 124 for use tolocate the points on the body in block 126.

At block 132, the surgical procedure is started and tracking anddisplaying of the surgical tool 12 is performed. The steps of trackingthe surgical tool 12 and showing the position of the surgical tool 12 onthe display device 24 are performed in accordance with the methodpreviously disclosed herein. Thereafter, the computer processing unit 22shows a representation of the position of the surgical tool 12 inrelation to the scan image 48 on the display device 24. In this manner,as the surgical tool 12 is manipulated within the surgical area, thesurgeon can see on a video monitor, for example, the position of thesurgical tool 12 with respect to interior portions of the patient's headin real time and thereby navigate the surgical tool 12 to a desiredlocation therein, such as the target location 62. Such navigation may beparticularly useful when, for example, the target location 62 is plannedand identified in the scan image 48 and the navigation system showswhere the surgical tool 12 is located in relation to that targetlocation 62.

FIGS. 6 and 7 show another embodiment of the navigation system 10 and adifferent use location on the patient's body. In FIG. 6, a cameraassembly 16 is shown attached to the back of the patient 20 in a fixedposition above the patient's spine. The camera assembly 16 is positionedsuch that the field of view of the camera 18 is pointing upwardly awayfrom the patient's back in order to be able to view the surgicalinstrument 12 during a spinal surgical procedure. As shown in FIG. 7,the camera assembly 16 is substantially similar to the camera assembly16 in FIG. 1 in that it includes a camera 18 attached in a fixedorientation and position on a resilient base plate 38, and adhesive 40carried by the base plate 38 is used to fixedly attach the base plate 38to the skin of the patient 20. In this embodiment, however, additionalattachment means in the form of pins 68 are used to provide additionalattachment functionality to the patient 20. The pins 68 extend at anangle through the resilient base plate 38, which may include pre-cutholes 70 adapted for directing the pins in a preselected direction, orthe pins 68 may be simply inserted through the resilient base plate 38without predefined holes therefor. The pins 68 are then driven and/orscrewed into a bone or an underlying bone, such as a vertebra 72 asshown in FIG. 7. All the remaining aspects of the camera assembly 16 andmethod of using the camera assembly 16 are the same as previouslydescribed with other embodiments herein. The camera assembly 16 is notlimited to use with the spinal cord or attachment to the vertebra 72,but the pins 68 may be used in other locations to attach or to provideadditional attachment functionality by screwing the pins 68 intodifferent bones underneath the skin of a patient 20. By using the pins68, the position of the camera 18 may be fixed in relation to underlyingbony structure at locations on the patient 20 where there is substantialsoft tissue, such as muscles, tendons, and/or organs underneath theskin, such as at a leg, in the back, or an arm, etc., where suchintervening soft tissue may allow an undesirably large amount ofmovement of the camera 18 on the skin in relation to more fixed bonystructures thereunder.

The navigation system 10 in another embodiment may be adapted to includemore than one camera 18. The cameras 18 are attached to the patient 20in a fixed position in the same manner as described previously.Preferably, two or more cameras 18 are also disposed in a fixed, knownposition in relation to each other, such as by being fixedly attached tothe base plate 38 in a known and/or pre-selected orientation. Thedifferent cameras 18 may be focused toward different viewing areasaround the patient 20 so that the fields of view of the cameras do notoverlap or only overlap partially and thereby provide a larger region inwhich navigation is available. In another embodiment, two spaced-apartcameras 18 are focused on the same viewing area and provide stereoviewing and navigation capabilities, from which navigation bytriangulation by known methods is possible. In this embodiment,registration and tracking is preferably performed in accordance withknown methods, either as described herein or as known otherwise forstereoscopic navigation processes. Stereoscopic navigation may providemore precise localization tracking with better accuracy for distanceperception, and allows for three-dimensional tracking of a single markin space, such as with a single LED or optical navigation marker 30.Stereoscopic navigation also makes it possible to work with incompleteform factor information of the optical navigation markers.

INDUSTRIAL APPLICABILITY

The navigation system 10 described herein in its various forms is usefulfor providing navigation information to a surgeon, for example, duringan surgical procedure and has several advantages over various surgicalnavigation systems of the prior art. One advantage is that by securelyattaching the camera 18 to the patient 20 in a fixed position, it ispossible to merge the camera space with the patient space and therebyeliminate the need for a separate patient tracker as used in many priorart systems. Eliminating the use of a separate patient tracker alsoeliminates at least one set of positional vectors that must beconcatenated in order to track the position of the surgical tool 12 withrespect to the patient 20 in a scan image 48 of the patient. Thus, incomparison to prior navigation systems, the present navigation system 10reduces the amount of computing resources needed to track the surgicaltool 12. Another advantage of the navigation system 10 over the priorsystems is that separating the camera 18 from the surgical tool 12allows a single camera 18 to be used to track more than one surgicaltool. In addition, a single camera 18 or set of cameras may be used withmany different surgical tools at once or in succession if the trackingelement 14 includes unique tool identification information readable bythe camera 18 and digital image recognition module 54. An additionalbenefit of the navigation system 10 is that there are no wires that haveto be attached to the surgical tool 12 in order to enable the navigationsystem 10, whereas a system that includes cameras on the tool generallymay need wires to provide an acceptable data communication link betweenthe camera and the computer processor. In addition, the navigationsystem 10 may easily be adapted to navigate surgical tools in manydifferent types of surgical procedures and is not limited to a singlesurgical procedure or even a predefined set of surgical procedures.Rather, the navigation system 10 may be easily adapted to providenavigation in almost any type of surgical procedure.

Numerous modifications to the present invention will be apparent tothose skilled in the art in view of the foregoing description.Accordingly, this description is to be construed as illustrative onlyand is presented for the purpose of enabling those skilled in the art tomake and use the invention and to teach the best mode of carrying outsame. The exclusive rights to all modifications which come within thescope of the appended claims are reserved. All patents, patentapplications, and other printed publications identified in thisforegoing are incorporated by reference in their entireties herein.

1. A surgical navigation system comprising: a camera including means forattaching the camera in a fixed position to a patient; a surgical toolincluding a tracking element readable by the camera; a computerprocessing unit comprising means for recognizing the tracking element inan image obtained by the camera and means for tracking the position ofthe surgical tool; a communication link adapted to transmit images fromthe camera to the computerized processing unit.
 2. The surgicalnavigation system of claim 1, wherein the means for attaching comprisesan adhesive.
 3. The surgical navigation system of claim 2, wherein themeans for attaching comprises a resilient base plate, wherein the camerais disposed on one side of the base plate and the adhesive is disposedon an opposite side of the base plate.
 4. The surgical navigation systemof claim 1, wherein the means for attaching comprises a pin adapted toattach the camera to a bony structure.
 5. The surgical navigation systemof claim 1, wherein the camera further comprises one or more fiducialmarkers sufficient to define a position of the camera, wherein thefiducial markers are disposed in a known pre-defined spatialrelationship with respect to the camera, and wherein the computerprocessing unit further comprises means for registering the position ofthe camera from the position of the fiducial markers with an image of apatient.
 6. The surgical navigation system of claim 5, wherein thecamera has a completely known optical geometry.
 7. The surgicalnavigation system of claim 1, wherein the surgical navigation systemcomprises a second camera associated with the means for attaching thecamera in a fixed position to the patient and in communication with thecomputer processing unit.
 8. The surgical navigation system of claim 1,wherein the tracking element comprises an optical pattern from which themeans for recognizing can identify the surgical tool and calculate theposition of the surgical tool.
 9. The surgical navigation system ofclaim 8, wherein the optical pattern comprises a localization patternand an identification pattern.
 10. The surgical navigation system ofclaim 9, further comprising a second surgical tool including a secondtracking element, wherein the second tracking element comprises thelocalization pattern and a different second identification pattern. 11.The surgical navigation system of claim 1, wherein the means fortracking is adapted to track the position of the surgical tool withrespect to a patient by directly concatenating a positional vector fromthe surgical tool to the camera without concatenating a positionalvector from a camera to a separate patient tracker.
 12. A surgicalnavigation camera comprising: a camera having a known focus; and meansfor attaching the camera in a fixed position to a patient.
 13. Thesurgical navigation camera of claim 12, further comprising: fiducialmarkers associated in a fixed pre-defined position with respect to thecamera.
 14. The surgical navigation camera of claim 13, wherein thecamera has a fixed focus.
 15. The surgical navigation camera of claim13, wherein the fiducial markers are disposed on a body of the camera.16. The surgical navigation camera of claim 13, wherein the fiducialmarkers are disposed on the means for attaching.
 17. The surgicalnavigation camera of claim 16, wherein the means for attaching comprisesa resilient base plate fixedly attached to the camera and adhesive onthe base plate.
 18. The surgical navigation camera of claim 12, whereinthe means for attaching comprises pins adapted to be attached to thebase plate and inserted into bone of the patient.
 19. The surgicalnavigation camera of claim 12, wherein the camera includes a validationand calibration feature in a known position in relation to the focus.20. A method of tracking a surgical tool with respect to a patient, themethod comprising the steps: attaching a camera to the patient in afixed position; tracking a position of the surgical tool in relation tothe patient using pictures taken by the camera and a computerizednavigation system.
 21. The method of claim 20, further comprising thestep: displaying on a display device the position of the surgical toolwith respect to the patient superimposed and in correlation with a scanimage of the patient.
 22. The method of claim 21, wherein the scan imageincludes an image of the camera on the patient, the method furthercomprising the step: automatically registering a position of the camerawith the scan image of the patient from the image of the camera and adatabase of form factor information about the camera.
 23. The method ofclaim 20, further comprising the steps: registering a position of thecamera with a scan image of the patient; validating the surgical tool;and optionally calibrating the surgical tool.